The logic illustrated in FIG. 7 may take place at the same frequency with which the polarization hopping changes (e.g., the operations illustrated in FIG. 7 may repeat at a time interval of T_hop as illustrated in FIG. 3). Accordingly, even if the jammer is performing polarization hopping, the jamming will only “match” the polarization of the transmitting signal, on average, 50 percent of the time because the jammer will not know the hopping sequence, and due to the correlation techniques used to retrieve the navigation codes, the navigation system may still operate successfully. Specifically, losing half of the hops is equivalent to a 3 dB loss in signal power, whereas a conventional receiver would be degraded by much more than this amount in jamming. When the jammer is on the opposite polarization, its energy will be rejected by a degree commensurate with the cross-polarization isolation (“XPI”). For a typical circular polarized antennas, XPI is between 20 to 25 dB. Accordingly, on average, receiver performance will have improved by the XPI—3 dB, resulting in a net anti-jamming improvement of 17 to 22 dB.
